Stray Flux Monitoring for Reliable Detection of Rotor Faults Under the Influence of Rotor Axial Air Ducts

Monitoring of induction motor faults based on stray flux measurement has been investigated by many researchers due to its potential benefits in cost and simplicity. Although it was shown that flux-based monitoring can provide sensitive fault detection comparable to that of motor current signature analysis, the lack of “remote” monitoring capability has limited its practical use. The performance and reliability of stray flux-based detection of induction motor rotor cage faults are evaluated in this paper. It is shown for the first time in this work that the spectrum analysis of the radial stray flux can provide reliable detection of rotor faults immune to the influence of rotor axial air ducts, which is the most common cause of false rotor fault alarms. The reliability and sensitivity of stray flux-based rotor fault detection are demonstrated through experimental testing on laboratory and 6.6 kV field motors.